Orthogonal frequency-division multiplexing (OFDM) is a method of encoding digital data on multiple carrier frequencies that has developed into a popular scheme for wideband digital communications. Some challenging issues remain unresolved in the design of the OFDM systems, including the high Peak-to-Average Power Ratio (PAPR) of transmitted OFDM signals. Most radio systems employ a high power amplifier (HPA) in the transmitter to obtain sufficient transmissions power and the HPA is usually operated at or near the saturation region to achieve the maximum output power efficiency. Accordingly, nonlinear distortion due to high PAPR of the input signals can be introduced into the communication channels. If the HPA is not operated in linear region with large power back-off, it is difficult to keep the out-of-band power below the specified limits. This situation can lead to very inefficient amplification and expensive transmitters.